This seems to be a popular complaint with the eight speed, a class action suit (you know the kind that keeps lawyers rich) has been filed against GM. Most dealerships will place a different fluid in the transmission if they can duplicate the “shudder”.
I have a 2016, dealer stated that GM was working on a fix for this, last December! Dealer I go to, HAS TO DUPLICATE EVERYTHING, or they do not fix anything! So I go to GMC Customer Service! Then the dealer will call and say"you should have come in and talked to us"! Really? In three years I have had three issues, of which only two were fixed because I got GMC involved! Next nearest dealer is 70 miles away! Toyota dealer is 50 miles away, of which I state to the service manager! His reply, "that is up to you" To a guy who has purchased over 20 new GM's over my lifetime! One of which was in March of this year!
YES! My 2016 was the most confused vehicle I have ever owned. It couldn't commit to a gear and when you pressed down the accelerator ir would shudder, bog and when it finally figured out what to do it would break your neck. Only vehicle I ever seen that slowed down when you pressed the gas to pass someone on the interstate. I traded it for a full size V6 Ram 1500. Bigger, more conformable and gets better MPG and smooth as silk. The GMC was the most disappointing car purchase I have made in 50 years. Sure was pretty though. The dealer grinned and said....Just be glad you don't have the 8 speed...its even worse!